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Flashcards in Proteins Deck (30):
1

What is released when a peptide bond is formed?

Water

2

What is the primary structure of a protein

The sequence of amino acids

3

What is the secondary structure of a protein?

The spatial arrangement of amino acid residues that are near each other in the linear sequence

4

What are the two structural forms of the secondary structure?

Alpha helix, beta sheets

5

What stabilises the alpha helix structure?

H bonds between the NH groups and the CO groups in the next turn of the helix

6

What stabilises the beta sheets?

H bonds between the amide groups of the linear polypeptide chains

7

What is the tertiary structure?

The spatial arrangements of amino acids residues that are far apart in the linear sequence

8

What is the tertiary structure held together by?

Van der waals forces
Ionic interactions
Hydrogen bonds
Disulphide bridges
Hydrophobic interactions

9

Where do ionic interactions take place?

Between two oppositely charged R groups

10

What environment is needed for intra polypeptide hydrophobic interactions to occur?

An environment within proteins from which water is excluded

11

Where do disulphide bridges occur?

They are strong covalent bonds that occur between two cysteine residues
They are common in extra-cellular proteins
They can occur between as well as within a polypeptide

12

What is the quaternary structure?

The spatial arrangement of individual polypeptide chains in a multi-subunit protein

13

What structure remains in tact after denaturation?

The primary structure

14

What are common causes of denaturation?

Acids
Heat
Solvents (ethanol)
Cross linking reagents (formaldehyde)
Chaotropic agents (urea)
Disulphide bond reducers (2 mercaptoehanol)

15

What is the effect of denaturation?

Decrease in solubility
Altered water binding capacity
Loss of biological activity
Improved digestibility

16

What is glycosylation?

Post translational modification whereby a sugar molecule binds via an amino acid to the protein

17

Give an example of a glycoprotein

Immunoglobulins

18

Where does glycosylation occur?

In the ER and the golgi apparatus

19

What is the roles of glycosylation?

Protein stabilisation
Affects solubility
Protein orientation
Signalling
Cell recognition

20

What is the function of lipoproteins?

Transport of water, insoluble fats and cholesterol in the blood

21

What are metalloproteins?

Protein molecule with a bound metal ion

22

What are the functions of metalloproteins?

Enzymes
Storage
Signalling
Transport

23

Why does haemoglobin have four subunits?

The binding of O2 to one sub unit alters its shape
This in turn causes a change in shape of the other sub-units so that they bind O2 more easily

Co-operative binding

24

How does sickle cell anaemia arise?

Substitution of one amino acid, hydrophilic Glutamic acid is replaced with hydrophobic amino acid Valine

25

What are the clinical features of sickle cell anaemia?

Severe haemolytic anaemia
Oxygen is given up more easily in the tissues

26

What is the structure of collagen?

Polypeptides coil to form a helix

Held together by hydrogen bonds
Interactions form fibrils which increases strength

27

What is the effect of scurvy?

Vitamin C deficiency, there is less hydroxyproline and hydroxylysine which are essential in stabilising cross links between chains of collagen, so collagen produced is weaker

28

What is the effect of osteogenesis imperfecta?

Protein cannot form into a tight coil due to amino acid substitution

There is less interaction between fibrils

Loss of secondary and tertiary structure

Weakened and brittle collagen is produced

29

What are the possible mutations of the LDL receptor?

No receptors produced
Receptors never reach cell surface
Receptors can't bind LDL
Receptors don't internalise on binding LDL
Receptors don't release LDL

30

What disease can result as an effect of LDL mutation?

Familial hypercholesterolemia, resulting in early cardiovascular disease